Some houses are provided with a roof window (may also be referred to as a skylight) for admitting sunlight. Many roof windows are of the type that cannot be opened and closed since they are often installed at locations that cannot be easily accessed. However, some roof windows are designed to be openable for ventilation, for example. Such an openable roof window may be opened and closed manually or may be driven electrically by an electric drive device in response to an operation performed by a user on an operation unit connected to the drive device wirelessly or by wire.
A variety of mechanisms for opening and closing a roof window have been proposed. For example, JP 63-27656A discloses an openable roof window including a base frame mounted to an opening formed in a roof, a movable window panel that is movable relative to the base frame to open and close the opening, and a pair of links rotatably connected to each other at intermediate portions thereof generally in a shape of a letter “X” and each having one end pivotably connected to one of the base frame and the movable window panel and the other end slidably received in a guide groove formed in the other of the base frame and the movable window panel, such that the base frame and the movable window panel are connected to each other via the pair of links. The distance from the one end of each link to the rotation axis is different from the distance from the rotation axis to the other end, whereby when the movable window panel is moved away from the base frame to open the opening, the movable window panel is tilted relative to the base frame.
Further, JP 61-94115 U discloses an openable roof window including a base frame mounted to an opening formed in a roof and a movable window panel having one end portion pivotably connected to the base frame, where the openable roof window is configured to prevent the movable window panel from being blown open by a strong wind beyond a desirable range, so that damage to the window panel caused by a strong wind can be avoided. The openable roof window disclosed in JP 61-94115 U includes a gas spring which connects the movable window panel to the base frame and prevents abrupt opening of the movable window panel. Specifically, one end of the gas spring is pivotably connected to one of the movable window panel and the base frame and the other end of the gas spring is pivotably connected to the other of the movable window panel and the base frame. The openable roof window disclosed in JP 61-94115 U further includes a rod member having one end portion pivotably connected to the movable window panel and the other end portion having an elongated hole formed therein to slidably receive a pin provided to the base frame, whereby the rod member limits the angular range of the pivoting movement of the movable window panel relative to the base frame in the opening direction.
However, in the conventional openable roof windows, the support stiffness of the movable window panel is not sufficient when the roof window is open. Specifically, in the openable roof window disclosed in JP 63-27656A, the movable window panel is supported only by the pair of links each consisting of an elongated rod member connected to the base frame and the movable window panel at the end portions thereof pivotably or slidably, and therefore, it is difficult to achieve sufficient support stiffness of the movable window panel. In the openable roof window disclosed in JP 61-94115 U, the movable window panel in the open state is supported by the gas spring and the rod member, each of which is pivotably connected to the movable window panel, and thus, the support stiffness of the movable window panel is low. Further, the opening and closing mechanisms disclosed in the foregoing prior art documents do not contribute to increase in the strength of the movable window panel. Moreover, the openable roof windows disclosed in these prior art documents are not configured to allow the movable window panel to slide relative to the base frame.